1. Technical Field of the Invention
This invention relates to a hermetic motor driven scroll apparatus, and more particularly to a lubricating mechanism for the hermetic motor driven scroll apparatus.
2. Description of the Prior Art
Hermetic motor driven scroll apparatuses are generally well-known. For example, in FIG. 4 of U.S. Pat. No. 5,247,738 to Yoshii, there is shown a hermetic type motor driven scroll compressor. Referring to FIG. 1, which is substantially identical to FIG. 4 of U.S. Pat. No. 5,247,738 to Yoshii, there is shown an overall construction of a hermetic type motor driven scroll compressor. For purposes of explanation only, the left side of FIG. 1 will be referred to as the forward end or front of the compressor and the right side of FIG. 1 will be referred to as the rearward end or rear of the compressor.
The hermetic type motor driven scroll compressor 100 comprises a compressor housing 11, which houses a compression mechanism 20. Compression mechanism 20 is a scroll-type fluid compression mechanism. A drive mechanism 30 is also housed within housing 11. Housing 11 comprises cylindrical portion 111 and first and second cup-shaped portions 112 and 113. An open end of first cup-shaped portion 112 is releasably and hermetically connected to a front open end of cylindrical portion 111 by a plurality of bolts 12. An open end of second cup-shaped portion 113 is releasably and hermetically connected to a rear open end of cylindrical portion 111 by a plurality of bolts 13.
Scroll-type fluid compression mechanism 20 comprises fixed scroll 21 having circular end plate 21a and spiral element 2lb, which rearwardly extends from circular end plate 21a. Circular end plate 21a of fixed scroll 21 is fixedly disposed within first cup-shaped portion 112 by a plurality of bolts 14. Compression mechanism 20 further comprises orbiting scroll 22 having circular end plate 22a and spiral element 22b, which forwardly extends from circular end plate 22a. Spiral element 21b of fixed scroll 21 interfits with spiral element 22b of orbiting scroll 22 with an angular and radial offset.
Seal element 211 is disposed at an end surface of spiral element 21b of fixed scroll 21, thereby sealing the mating surfaces of spiral element 21b of fixed scroll 21 and circular end plate 22a of orbiting scroll 22. Similarly, seal element 221 is disposed at an end surface of spiral element 22b of orbiting scroll 22, thereby sealing the mating surfaces of spiral element 22b of orbiting scroll 22 and circular end plate 21a of fixed scroll 21. O-ring seal element 40 is elastically disposed between an outer peripheral surface of circular end plate 21a of fixed scroll 21 and an inner peripheral surface of first cup-shaped portion 112 to seal the mating surfaces therebetween. Circular end plate 21a of fixed scroll 21 partitions an inner hollow space of compressor housing 11 into discharge chamber 50 and suction chamber 60.
Circular end plate 21a of fixed scroll 21 is provided with valved discharge port 21c axially formed therethrough so as to link discharge chamber 50 to a central fluid pocket (not shown), which is defined by fixed and orbiting scrolls 21 and 22. First cup-shaped portion 112 has cylindrical projection 112a forwardly projecting from a central region of an outer surface of a front end section thereof. Compressed refrigerant fluid is discharged from the central fluid pocket through valved discharge port 21c and into discharge chamber 50. Discharge chamber 50 is connected to an external cooling circuit (not shown) through axial hole 112b. Axial hole 112b, which functions as an outlet port of compressor 10, is formed through cylindrical projection 112a so as to be connected to an inlet of an element (not shown), e.g., condenser of the external cooling circuit through a pipe member (not shown).
Drive mechanism 30 comprises drive shaft 31 and motor 32 for rotating drive shaft 31. Drive shaft 31 comprises pin member 31a, which forwardly extends from, and is integral with, a front end surface of drive shaft 31. An axis of pin member 31a is radially offset from an axis of drive shaft 31. Bushing 311 is rotatably disposed within annular projection 22c, which axially projects from a central region of the rear end surface of circular end plate 22a of orbiting scroll 22, through radial needle bearing 312. Bushing 311 includes a small cylindrical projection (not shown) which is formed at a rear end surface thereof. A longitudinal axis of the small cylindrical projection is radially offset from a longitudinal axis of bushing 311 by a predetermined distance, such as the radius of circular orbit which is created during the orbital motion of orbiting scroll 22. The small cylindrical projection of bushing 311 is loosely received within a small cylindrical depression (not shown) which is formed at the from end surface of drive shaft 31. Shallow depression 311a is formed at a front end surface of bushing 311. Balance weight 313 is fixedly disposed on a rearward extension of bushing 311 and serves to balance the torque of drive shaft 31. Pin member 31a is rotatably inserted in an axial hole 311b of bushing 311 to operatively connect pin member 31a to circular end plate 22a of orbiting scroll 22. The axis of hole 311b is radially offset from the axis of bushing 311. Relative axial movement between pin member 31a and bushing 311 is prevented by snap ring 314 which is fixedly mounted about a front end portion of pin member 31a.
Inner block 23 extends radially inwardly from, and is integral with, the front end of cylindrical portion 111 of compressor housing 11. Rotation preventing mechanism 24 is disposed between inner block 23 and circular end plate 22a of orbiting scroll 22 so that orbiting scroll 22 only orbits during rotation of drive shaft 31. Inner block 23 comprises a central hole 23a of which the longitudinal axis is aligned with the longitudinal axis of cylindrical portion 111. Bearing 25 is fixedly disposed within central hole 23a so as to rotatably support a front end portion of drive shaft 31. Inner block 23 partitions suction chamber 60 into first suction chamber section 61 rearward of inner block 23 and second suction chamber section 62 forward of inner block 23. A plurality of holes 35 are axially formed through inner block 23 to link first and second suction chamber sections 61 and 62.
Second cup-shaped portion 113 comprises annular cylindrical projection 113a forwardly projecting from a central region of an inner surface of a rear end section thereof. The longitudinal axis of annular cylindrical projection 113a is aligned with the longitudinal axis of second cup-shaped portion 113. Bearing 26 is fixedly disposed within annular cylindrical projection 113a so as to rotatably support a rear end portion of drive shaft 31. Second cup-shaped portion 113 further comprises cylindrical projection 113b rearwardly projecting from a central region of an outer surface of the rear end section thereof. Axial hole 113c, which functions as an inlet port of compressor 10, is formed through cylindrical projection 113b and is connected to an outlet of another element (not shown), e.g., an evaporator of the external cooling circuit, through a pipe member (not shown). The longitudinal axis of axial hole 113c is aligned with the longitudinal axis of annular cylindrical projection 113a. A diameter of axial hole 113c is slightly smaller than an inner diameter of annular cylindrical projection 113a.
First annular cut-out section 15 is formed at an inner periphery of an open end surface of first cup-shaped portion 112 of compressor housing 11. Consequently, first annular projection 15a is formed at an outer periphery of the open end surface of first cup-shaped portion 112. The longitudinal axis of an inner periphery of first annular projection 15a is aligned with the longitudinal axis of first cup-shaped portion 112. Second annular cut-out section 16 is formed at an outer periphery of a front open end surface of cylindrical portion 111 of compressor housing 11. Consequently, second annular projection 16a is formed at an inner periphery of the front open end surface of cylindrical portion 111. The longitudinal axis of an outer periphery of second annular projection 16a is aligned with the longitudinal axis of cylindrical portion 111. By the above described construction, the open end of first cup-shaped portion 112 and the front open end of cylindrical portion 111 are connected to each other by a faucet joint. O-ring seal element 41 is elastically disposed at a rear end surface of first annular cut-out section 15 to seal the mating surfaces of first annular cut-out section 15 and second annular projection 16a.
Third annular cut-out section 17 is formed at an inner periphery of a rear open end surface of cylindrical portion 111 of compressor housing 11. Consequently, third annular projection 17a is formed at an outer periphery of the rear open end surface of cylindrical portion 111 of compressor housing 11. The longitudinal axis of an inner periphery of third annular projection 17a is aligned with the longitudinal axis of cylindrical portion 111. Fourth annular cut-out section 18 is formed at an outer periphery of an open end surface of second cup-shaped portion 113 of compressor housing 11. Consequently, fourth annular projection 18a is formed at an inner periphery of the open end surface of second cup-shaped portion 113. The longitudinal axis of the outer periphery of fourth annular projection 18a is aligned with the longitudinal axis of second cup-shaped portion 113. By the above-described construction, the open end of second cup-shaped portion 113 and the rear open end of cylindrical portion 111 are connected to each other by a faucet joint. O-ring seal element 42 is elastically disposed at a rear end surface of third annular cut-out section 17 to seal the mating surfaces of third annular cut-out section 17 and fourth annular projection 18a.
Drive shaft 31 further comprises first axial bore 31b axially extending therethrough. One end of first axial bore 31b is open at a rear end surface of drive shaft 31 so as to be adjacent to a front open end of axial bore 113c. The other end of first axial bore 31b terminates at a position which is behind bearing 25. A plurality of radial bores 31c are formed at a front terminal end of first axial bore 31b so as to link the from terminal end of first axial bore 31b to first suction chamber section 61. Second axial bore 31d axially extends from the front terminal end of first axial bore 31b and is open at a from end surface of pin member 31a of drive shaft 31. The diameter of second axial bore 31d is designed to be smaller than the diameter of first axial bore 31b. The longitudinal axis of second axial bore 31d is radially offset from the longitudinal axis of first axial bore 31b.
Annular cylindrical projection 113d rearwardly projects from a peripheral region of the outer surface of the rear end section of second cup-shaped portion 113. One portion of annular cylindrical projection 113d is integral with one portion of cylindrical projection 113b. An insulating base 27 having external power conductor terminals 27a is firmly secured to a rear end of annular cylindrical projection 113d by a plurality of bolts (not shown). O-ring seal element 43 is elastically disposed at a rear end surface of annular cylindrical projection 113d so as to seal the mating surfaces of insulating base 27 and annular cylindrical projection 113d.
Motor 32 includes annular-shaped rotor 32a fixedly surrounding an exterior surface of drive shaft 31 and annular-shaped stator 32b surrounding rotor 32a with a small radial air gap. Stator 32b axially extends along the rear open end region of cylindrical portion 111 and the open end region of second cup-shaped portion 113. Stator 32b is disposed between a first annular ridge 111a formed at an inner peripheral surface of cylindrical portion 111 and a second annular ridge 113e formed at an inner peripheral surface of second cup-shaped portion 113. The axial length of stator 32b is slightly smaller than an axial distance between first annular ridge 111a and second annular ridge 113e.
In a process of assembling compressor 100, stator 32b is fixedly secured to the rear open end region of cylindrical portion 111 and to the open end region of second cup-shaped portion 113 by a shrinkage fit technique. According to this technique, stator 32b is inserted into the rear open end region of cylindrical portion 111, until an outer peripheral portion of a front end surface of stator 32b is in contact with a side wall of first annular ridge 111a, or stator 32b is inserted into the open end region of second cup-shaped portion 113, until an outer peripheral portion of a rear end surface of stator 32b is in contact with a side wall of second annular ridge 113e.
In operation, refrigerant fluid flowing from an outlet of one external element (not shown), e.g., an evaporator, is conducted into axial hole 113c and then flows through first axial bore 31b of drive shaft 31. A portion of the refrigerant fluid in first axial bore 31b flows into first suction chamber section 61 through radial bores 31c, and then further flows into second suction chamber section 62 through holes 35 of inner block 23. The remainder of the refrigerant fluid in first axial bore 31b of drive shaft 31 flows through second axial bore 31d, and then flows into a hollow space 63 which is defined by circular end plate 22a of orbiting scroll 22, annular projection 22c and bushing 311. A portion of the refrigerant fluid in hollow space 63 flows to second suction chamber section 62 past the internal gaps of radial needle bearing 312, and the gaps created between radial needle bearing 312 and annular projection 22c and between radial needle bearing 312 and bushing 311. Therefore, the internal frictional surfaces between radial needle bearing 312 and annular projection 22c and the frictional surfaces between radial needle bearing 312 and bushing 311 are lubricated by, for example, lubricating oil suspended in the refrigerant fluid in a mist state. The remainder of the refrigerant fluid in hollow space 63 flows into second suction chamber section 62 past the small air gaps created between snap ring 314 and bushing 311, between pin member 31a and bushing 311, between bushing 311 and balance weight 313, and between balance weight 313 and the from end surface of drive shaft 31. Therefore, the frictional surfaces between snap ring 314 and bushing 311 and between pin member 31a and bushing 311 are lubricated by the lubricating oil which is suspended in the refrigerant fluid in a mist state.
The refrigerant fluid flowing through radial bores 31c and the refrigerant fluid flowing through second axial bore 31d are merged at second suction chamber section 62, and then are taken past the rotation prevention mechanism 24, then into the outer sealed-off fluid pockets defined by the fixed and orbiting scrolls 21 and 22. Therefore, the internal frictional surfaces of rotation preventing mechanism 24 are lubricated by the lubricating oil which is suspended in the refrigerant fluid in a mist state. The refrigerant fluid taken into the outer sealed-off fluid pockets travels centrally with decreasing volume thereof, e.g., with compression thereof, in accordance with an orbital motion of orbiting scroll 22. The compressed refrigerant fluid is then discharged into discharge chamber 50 through valved discharge port 21c of circular end plate 21a of fixed scroll 21. The refrigerant fluid in discharge chamber 50 flows through axial hole 112b to an inlet of another external element (not shown), e.g., a condenser.
According to the foregoing conventional compressor, second axial bore 31d axially extends from the front terminal end of first axial bore 31b such that the longitudinal axis of first axial bore 31b is located outside the longitudinal axis of the second axial bore 31d. Due to this arrangement, the refrigerant fluid inefficiently flows from the first axial bore 31b to the second axial bore 31d during operation of the compressor. Consequently, a relatively small amount of the lubricating oil is conducted into hollow space 63 through second axial bore 31d. As a result, the frictional surfaces between bushing 311 and the elements associated with the busing 311, such as pin member 31a and radial needle bearing 312, are sometimes insufficiently lubricated during operation of the compressor.